I have pretty much the same wet/dry, just bigger, and you shouldnt have any bubbles coming out??? they still would have to go over the blue pad, through your Bio Balls, through the Polishing sponge and back to the tank, there should be No bubbles! Is your filter set up right ??? I would check it and make sure it is. And one important thing, is your water level above the return pump??? That will cause micro bubbles and is usually the culprit. Let us know Todd